I believe most PD's in the US used the Springfield Armory in the recent past.
However, there seems to be a shift towards the Sig's and Ruger's as of late. My understanding is that they had to upgrade to "compete" with the criminal underworld that has out-gunned them for quiet some time now.

having said that, the Springfield Armory XD-40 ought to serve us,private citizens, well.
STICK WITH WHAT WORKS FOR YOU!

I have to agree the springfield is a very fine weapon. I have the XD45 tactical (5") shoots nice double stack. when my son was 14 yo he cut on ragged hole at 7 yards with it. that said the 5" is a bit much for conceal carry so i carry a glock 30. its also 45acp but like a 3ish" barrel and crimson trace laser grip.